George was born in Hanover, in what is now Germany, and inherited the titles and lands of the Duchy of Brunswick-Lüneburg from his father and uncles. A succession of European wars expanded his German domains during his lifetime, and in 1708 he was ratified as prince-elector of Hanover. At the age of 54, after the death of Queen Anne of Great Britain, George ascended the British throne as the first monarch of the House of Hanover. Although over fifty Roman Catholics bore closer blood relationships to Anne, the Act of Settlement 1701 prohibited Catholics from inheriting the British throne; George was Anne's closest living Protestant relative. In reaction, Jacobites attempted to depose George and replace him with Anne's Catholic half-brother, James Francis Edward Stuart, but their attempts failed.

During George's reign, the powers of the monarchy diminished and Britain began a transition to the modern system of cabinet government led by a prime minister. Towards the end of his reign, actual power was held by Sir Robert Walpole, now recognised as Britain's first de factoprime minister. George died on a trip to his native Hanover, where he was buried.

The source states that the birth date for George I is often reported as 7 June 1660 in many English historical accounts owing to the use of the Gregorian calendar; however, as of 1660, the Julian calendar remained in use in England.